24. Enolate Chemistry: Reactions at the Alpha-Carbon

Provide the major product after each step for the following reaction.

Which of the following can NOT be formed through the stork enamine reaction with 2-butanone? 

Describe how the following compounds could be prepared from cyclohexanone using an enamine intermediate:

b.

Write equations showing the expected products of the following enamine alkylation and acylation reactions. Then give the final products expected after hydrolysis of the iminium salts.

(a) pyrrolidine enamine of pentan-3-one + allyl chloride

(b) pyrrolidine enamine of acetophenone + butanoyl chloride

Without looking back, propose a mechanism for the hydrolysis of this iminium salt to the alkylated ketone. The first step is attack by water, followed by loss of a proton to give a carbinolamine. Protonation on nitrogen allows pyrrolidine to leave, giving the protonated ketone.

Write equations showing the expected products of the following enamine alkylation and acylation reactions. Then give the final products expected after hydrolysis of the iminium salts.

(c) piperidine enamine of cyclopentanone + methyl iodide

Describe how the following compounds could be prepared from cyclohexanone using an enamine intermediate:

a.

What reagents should be used to prepare the following compounds?

c.

Show how you would accomplish each conversion using an enamine synthesis with pyrrolidine as the secondary amine.

(c)

Predict the products of the following reactions.

(e)